symPACK is a package for the direct solution of sparse symmetric positive definite systems of linear equations. The routines perform an LL^T (or LDL^T without pivoting) decomposition and triangular solutions through forward and back substitutions. Capabilities include asynchronous task-based computation, matrix column reordering and relative backward error calculation.

Usage and applications: symPACK is the default solver used in the preprocessing step of the Parallel Selected Inversion implemented in Pole EXpansion and Selected Inversion (PEXSI) package, which is included in multiple electronic structure calculation packages, such as SIESTA and CP2K. symPACK and PEXSI have recently been incorporated into the ELectronic Structure Infrastructure (ELSI) library, which is an NSF effort providing a common interface to multiple software libraries used in electronic structure calculations in materials science. It has been used by several DOE application codes, including DGDFT, and is used in the current BES SciDAC application partnership projects.